The 2015 ISIS video showing the beheadings of 21 Egyptian Coptic Christians on a beach in Sirte, Libya was one of its most brutal. It featured an English-speaking spokesman who sounded American. One of the big mysteries was his identity -- and which beach the killings occurred on.

The "full details" of the slaughter seem to mostly have been supplied by detainees under interrogation. One says he was located behind the camera as it was being filmed. The story is available on the group's Facebook page, in Arabic. The translation on FB is terrible. The beach is the one behind the Mahari hotel in Sirte (the same one where 50 plus Gaddafi followers were killed in 2011.)

Libyan authorities said Saturday that they recovered the remains of Coptic Christians killed in Libya in February 2015 by Islamic State militants.

The remains were transferred to the forensics lab in Misrata city for DNA testing, in order to deliver the remains over to families of the victims.

Libya’s Public Prosecution announced last month that the perpetrators of the kidnapping and beheading of the 21 Copts were arrested, after authorities discovered the murdered Egyptians in Sirte, Libya.

The Bunyan Marsoos Operation, which was the force that defeated ISIS in their main city of Sirte, said in a statement issued today that after interrogating ISIS prisoners who were captured after the war, they were able to identify and question one of the eyewitnesses and perpetrators of the horrifying event.

The witness provided, according to the Media Office, accurate details of the bloody day and the names of some of the executors. He also provided the name of the director of brutal video and the site in which the massacre was carried out, in addition to the burial site of bodies in the area of Khashoum Khail, south of Sirte.

The Media Office added that it was this admission and statement that led the Attorney General's Office to the burial place of corpses, which were exhumed on Friday morning to complete DNA tagging procedures then later deliver the deceased to their relatives.